#10-24 UNC Thread
Direct Answer
10-24 UNC is a numbered Unified Coarse machine screw thread with a major diameter of 0.1900 inches (4.826 mm) and 24 threads per inch (TPI). Requiring a #25 (0.1495 inch) tap drill, it provides high clamping torque for household appliances, outdoor power equipment, and light mechanical assemblies.
Source: ANSI/ASME B1.1
Specs
| Nominal Major Diameter | 0.1900 in (4.826 mm) |
| Threads Per Inch (TPI) | 24 TPI (Coarse pitch: 1.058 mm) |
| Fine Pitch Equivalent | #10-32 UNF (0.794 mm pitch — widely used in 19" AV racks) |
| Tap Drill Size (UNC) | #25 drill bit (0.1495 in / 3.80 mm) |
| Tap Drill Size (#10-32 UNF) | #21 drill bit (0.1590 in / 4.04 mm) |
| Minor Diameter (Internal) | 0.1449 in (3.680 mm) |
| Tensile Stress Area | 0.0175 in² (11.3 mm²) |
#10-24 UNC vs #10-32 UNF Rack Confusion
A classic engineering conflict exists between #10-24 UNC and #10-32 UNF. In North American server and AV equipment racks with pre-tapped rails (Middle Atlantic, Gator Cases), #10-32 UNF is standard. Attempting to force a coarse #10-24 screw into a fine #10-32 tapped rail will bind and strip the rack threads.